The Right Shift Theory Essay

649 Words Oct 26th, 2013 3 Pages
The Right Shift Theory
In 1972, Marian Annett of the University of Leicester UK proposed a theory that came to be known as the Right Shift Theory. She believed that as humans evolved, all of the major functions of the brain, such as speech, shifted to being controlled and centered in the left hemisphere of the brain, which controls the right side of the body naturally. By shifting important functions to the left, a bias for the right hand would be created. This lateralization and biased, according to the theory, is controlled by a gene, or a set of genes. More recent studies, specifically those of Dr. Amar J.S. Klar, agree with Annett on the assumption that the right-handed bias found in the population is caused by a set of genes. 20% of
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Duplicating processes in both hemispheres of the brain simultaneously wastes precious energy, so by way of evolutions processes such as speech have begun to develop on specific hemispheres of the brain. In 90-95% of right handed people, the left hemisphere is dominant for speech and language processes. The other 5% have verbal processes based in the right hemisphere, suggesting that the majority of the population follows the Mcmanus model. By following this theory, when lateralization begins in the early development of a human, a biased has been observed that the corresponding hand preference appears with strong favoritism to one hemisphere. The Mcmanus Model also acknowledges the strong influence that outside factors could have on an individual while developing their brain and hand preference.

Brain Pathology: Birth trauma/ Difficult pregnancies
Dr. Stanley Coren, a psychologist from the University of British Columbia in Vancouver, did extensive research and completed a novel on the causes of handedness. His experiments yielded a theory that is extremely different from all others. He explained right handedness as being the expected preference for all humans. Coren believes that everyone is supposed to be born with a right bias, but brain injury during development in the womb can cause right hemisphere lateralization, leading to left handedness. The only genetic theory that he acknowledges is the

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